Field of the Invention
The present invention relates to a quantum dot, and more particularly, to a method of manufacturing a quantum dot having a tunable and narrow light emission wavelength for achieving a high color purity and a method of manufacturing a film.
Description of the Related Art
Quantum dots (QDs) are semiconducting nano-sized particles having a three-dimensionally limited size and exhibit excellent optical and electrical characteristics that are not possessed by semiconducting materials in a bulk state. For example, the color of light emitted from quantum dots may vary depending on the particle size although the quantum dots are produced from the same substance. Because of such characteristics, quantum dots are attracting attention as next generation high-brightness light emitting diodes (LEDs), bio sensors, lasers, and solar cell nanomaterials.
Currently, non-hydrolytic synthesis is a commonly used manufacturing method for forming quantum dots. According to this method, quantum dots have been manufactured by rapidly injecting an organic metal compound at room temperature as a precursor into a solvent at a high temperature to produce nuclei by the thermal decomposition reaction and then increasing the temperature to grow the nuclei. The quantum dots to be mainly synthesized by this method contain cadmium (Cd) such as cadmium selenide (CdSe) or cadmium tellurium (CdTe). However, the use of cadmium (Cd), one of the representative environmental pollutants which pollute water and soil, is required to be minimized when the current trend of pursuing the green industry by heightened environmental awareness is taken into consideration.
Hence, it is considered to manufacture quantum dots of semiconductor material which does not contain cadmium as an alternative for replacing existing CdSe quantum dots or CdTe quantum dots, and indium phosphide (InP) quantum dots are one of these. InP quantum dots can replace the CdSe quantum dot material and be used in the manufacture of a high-brightness light emitting diode device and the like as the InP quantum dots can emit light in a visible light region which is a light emission region similar to that of the CdSe quantum dot material.
However, InP quantum dots have a disadvantage that it is not only difficult to mass-produce InP quantum dots since the synthesis thereof is generally difficult but also the uniformity of particle size is more hardly secured and the quantum yield (QY) is lower as compared with the existing CdSe quantum dot material.
As a measure to solve the above-mentioned disadvantages of InP quantum dots, there is a method in which a shell formed of a II-VI group compound having a band gap larger than that of the core such as zinc sulfide (ZnS) is coated on the surface of the InP core. It is possible to solve the problem that it is difficult to maintain the light emission stability or to control the size of the InP quantum dots, which is a III-V group compound, to a certain extent when the InP core is coated with a II-VI group compound shell having a band gap larger than that of the core. However, problems such as productivity (reaction time), manufacturing cost and environment (amount of sample, odor, and the like), and securement of coating uniformity are required to be sufficiently considered even when coating the shell. Not only the light emission efficiency of the quantum dots decreases but the light emission characteristics are significantly sensitive to the change of the surface molecules in some cases when the shell is not properly formed.